The UN engagement in civil wars was almost nonexistent until the end of the Cold War, but recent experience brings some important lessons: the traditional principles of peacekeeping are ill-suited for civil war, as demands on peacekeepers, in particular the protection of civilians, are expanding. But military force is there to support a political strategy. The UN must focus on politics, using its comparative advantage–its independence–to win the confidence of the parties, while preserving its access to big powers to put pressure on them. However, it is challenged by the growing divisions in the Security Council, the changing nature of conflict, and a crisis of states that reflects long-term trends. This is not a reason for the UN to abandon its role in ending civil wars, but it needs to recalibrate its ambitions and adapt its approach: be less state-centric and more inclusive; more robust militarily; and more disciplined in its priorities.